Gripping mechanism of vertical ingot chargers and similar machines



March 6, 1962 D. c. HENDRY 3,023,578

GRIPPING MECHANISM OF VERTICAL INGOT CHARGERS AND SIMILAR MACHINES- Filed Sept. 30, 1960 Inventor DA V/D CALDER Havmv a. w M

Attorney United States Patent 3,023,578 GRWPING WCHANISM OF VERTICAL INGOT CHARGERS AND SIMILAR MACHINES David Calder Hendry, Kettering, Northants, England,

assignor to Stewarts and Lloyds Limited, Glasgow,

Scotland Filed Sept. 30, 1960, Ser. No. 59,664 Claims priority, application Great Britain Nov. 20, 1959 2 Claims. (CI. 60-51) This invention relates to the gripping mechanism of vertical ingot charging cranes and similar machines by which hot ingots, blooms and the like are lowered into and retracted from soaking pits or similar furnaces.

The tongs of such machines must grip the work with considerable force, for which reason the tongs are generally operated by mechanical screw or cam action in conjunction with the hoisting gear.

A more suitable means of operation would be by hydraulic power, more especially having regard to the high loads and the short strokes involved; and hydraulic operation in conjunction with an accumulator would provide I a storage of energy enabling the tongs to retain the grip or to be independently actuated in the event of a power failure.

However, a very serious difliculty presents itself in connection with hydraulic operation of the gripping tongs bearing in mind that ingot charging cranes usually undergo long and cross travel, and that the mast carrying the tongs and their operating mechanism may be rotated as well as raised and lowered. It follows that the tong gripping mechanism in the mast head can not be rigidly connected to any substantial part of the crane, so that an hydraulic accumulator mounted for example on the crane bridge would involve the use of flexible hose of substantial length between it and the tong operating mechanism, and failure of any such hose would entail the discharge of the hydraulic liquid under certain conditions directly into the soaking pit or furnace with possible damage and danger to life and limb.

The present invention provides means for hydraulically operating the gripping tongs by which the stated difficulty and danger is avoided.

Said means for operating the gripping-tongs pull-rod comprises, in combination, a tank enclosing the upper end portion of the pull-rod; within the tank at least one hydraulic cylinder, and a piston slidable in the cylinder and rigidly connected with the pull-rod; a container superimposed on the tank; and within the container an hydraulic accumulator, a pump, an electric motor for driving the pump, a valve-controlled liquid supply pipe from the accumulator to the pump, a valve-controlled liquid supply pipe from the pump and accumulator to the cylinder in the subjacent tank, a return pipe leading from the last mentioned pipe to the tank, and stand-pipes encasing the pipe portions passing from the container to the tank.

By Way of example an embodiment of the invention is illustrated on the accompanying drawings whereon:

FIG. 1 is a part sectional elevation of this embodiment;

FIG. 2 is a cross section of a modification in the plane represented by II-1I in FIG. 1.

The self-contained hydraulic power unit illustrated includes a storage tank b of sufficient capacity to retain all the hydraulic liquid in the system at a level below the top of the central spigot m in which works the pull rod a. An annular hydraulic cylinder 0 surrounds the spigot, and has an annular piston 03 connected to the pull rod.

The lid of the tank b forms the base of a superimposed container h with a cover q housing a pump 1, an electric driving motor 2 and an accumulator g. The pump is con nected with the hydraulic cylinder 0 through piping i fitted with check valves l and s and an electrically operated 3,Z3,578 Patented Mar. 6, 1962 3-way control valve k. The return line from this valve is led to the tank and fitted with a filter r. Another pipe (not shown) leads from the interior of the tank b to the suction side of the pump 1.

When the motor e is switched on the pump 1 draws liquid from the tank b trough this last mentioned pipe and charges the accumulator g through a pipe connection p. When the pressure in the accumulator reaches the predetermined value a pressure switch (not shown) operates to switch off the motor e or by-pass the liquid from the pump delivery back to the tank. This part of the hydraulic circuit is henceforth automatic, i.e. the switch cuts in the motor or isolates the by-pass whenever the hydraulic pressure drops below the predetermined minimum and switches it off or opens the bye-pass at the predetermined maximum.

To operate the tongs the valve k is set to connect the accumulator g with the cylinder 0 causing the piston d and the rod :1 connected with the tongs to rise, so that the tongs move to grip the ingot. Engagement with the ingot prevents further closure of the tongs, so that the mechanical link motion ceases to move and the rod is thus prevented from rising further. The whole linkage then remains under static load, pressure being maintained under the piston d by the accumulator, and being transmited through the mechanism, increasing or decreasing according to the levers and cranks employed, and culminating in a static compressive grip on the ingot by the jaws of the tongs. Should leakage develop aforesaid pressure switch will operate to maintain the pressure. In this state the ingot will be gripped indefinitely.

To de-grip, i.e. to release the ingot the 3 way valve k is set so as to isolate the accumulator g from the cylinder 0 and also to connect the cylinder 0 with the tank. This allows the cylinder to be exhausted and the pressure to be maintained in the accumulator.

One or more ports (not shown) pass under the base of the cylinder c and are led up adjacent to the spigot In so that any leakage along the inner surface of the piston at will find its way by gravity back into the tank b. Further, a gland or similar packing is provided to seal between the rod a and the spigot m.

It should be noted that there are no joints or gaskets below the liquid level at which leakage might occur and that all piping passing through the lid of the tank b is encased by standpipes t so that leakage into the container h will collect by gravity in the lower part of this container and be positively constrained from finding its way into the tank b except via the valve 11.

Should a major leak occur, as for example the failure of a joint in the pressure pipe, the escaping liquid is prevented by the container h from being discharged into any zone of danger, such as the soaking pits. On the contrary, the liquid collects in said container and the hydraulic system becomes starved of liquid; hence pressure is no longer built up and the operator realises that a failure has occurred. A manually operable valve n in the lid of tank b allows the liquid to be drained back into said tank through the filter r when the trouble has been rectified. If required, the valve 11 may be locked in the open position so that small leakage, e.g. from the pump glands or the valve glands will be continuously filtered and returned to the tank.

A vent (not shown) is connected to the space above the filter r to vent the air displaced by the varying volume of liquid in the tank. This vent is situated at the top of a standpipe that rises above the level of any liquid in the container h. The filter r is of the basket type, readily removable for cleaning and with a large port near the top to allow overflow in the event of clogging.

It will thus be apparent that the unit is most compact and self-contained, it being merely necessary to supply electric current to the motor and to operate the valve it under manual control. There are no flexible hydraulic pipes and no pressurised components whose failure could leak the hydraulic liquid out of the system.

The described arrangement for hydraulically operating the gripping tongs of vertical ingot charging cranes and similar machines fulfil the following:

(a) In the event of pump failure the accumulator will supply suflicient hydraulic power for several operations;

(b) In the event of accumulator failure the non-return valve .5- will hold in the pressure in the ram cylinder, thus avoiding dropped ingots; (c) Should seepage occur at the valve or ram the system, within reasonable limits will maintain the pressure; (d) Any spraying liquid, from a broken connection for example, is wholly contained in the container h and is eventually diverted back to the liquid storage tank; and

(e) The totally enclosed nature of the unit will reduce evaporation to a minimum.

In FIG. 2 I show, instead of the annular cylinder c and annular piston d of FIG. 1, four (or it may be any other number) of circular cylinders and pistons d I claim:

1. Means for operating the gripping-tongs pull-rod of an ingot or like charging machine, comprising, in combination, a tank enclosing the upper end portion of the pullrod; within the tank at least one hydraulic cylinder, and a piston slidable in the cylinder and rigidly connected with the pull-rod; a container superimposed on the tank; and within the container an hydraulic accumulator, a pump, an electric motor for driving the pump, a valvecontrolled liquid supply pipe from the pump to the accumulator, a valve-controlled liquid supply pipe from the pump and accumulator to the cylinder in the subjacent tank, a return pipe leading from the last mentioned pipe to the tank, and standpipes encasing the pipe portions passing from the container to the tank.

2. Means for operating the gripping-tongs pull-rod of an ingot or like charging machine, comprising, in combination, a tank enclosing the upper end portion of the pullrod; within the tank a plurality of hydraulic cylinders, and a plurality of pistons slidable in the cylinders and rigidly connected with the pull-rod; a container superimposed on the tank; and within the container an hydraulic accumulator, a pump, an electric motor for driving the pump, a valve-controlled liquid supply pipe from the pump to the accumulator, a valve-controlled liquid supply pipe from the pump and accumulator to the cylinder in the subjacent tank, a return pipe leading from the last mentioned pipe to the tank, and standpipes encasing the pipe portions passing from the container to the tank.

References Cited in the file of this patent UNITED STATES PATENTS 1,411,348 Haeberlein Apr. 4, 1922 1,993,612 Lum Mar. 5, 1935 2,131,910 Vernon et a1. Oct. 4, 1938 2,379,304 Kalin June 26, 1945 2,679,854 Stevenson June 1, 1954 2,735,445 Ray et a1 Feb. 21, 1956 FOREIGN PATENTS 1,043,820 Germany Nov. 13, 1958 

